Fig. 3.

Phase diagram of the Al₂SiO₅ system using DFT-calculated standard enthalpy, entropy, and heat capacity values of this study compared to calculations with the Holland and Powell (2011) data set (HP11). The thick curve represents the breakdown reaction of kyanite to corundum + quartz (using the data set of Holland and Powell 2011). The shaded area shows the stability field of corundum + quartz, if DFT-based data are used for the Al₂SiO₅ phases. If internally consistent data sets are used instead, the coexistence of quartz + corundum is not possible